Besides fourth ranked Reliance Industries chairman Ambani and fifth placed steel czar Mittal, four other Indians were among top 50 in 2010 Forbes list of the World’s Billionaires released on Wednesday with as many 49 Indians joining company with the planet’s 1,011 richest people.

With his fortune swelling to an estimated $53.5 billion, up $18.5 billion in 12 months, Slim surged ahead of Microsoft cofounder Bill Gates, who had held the title of world’s richest for 14 of the past 15 years, the US business magazine noted.

Gates, now worth $53 billion, is ranked second in the world. He is up $13 billion from a year ago as shares of Microsoft rose 50 percent in 12 months. Buffett’s fortune jumped $10 billion to $47 billion on rising shares of Berkshire Hathaway. He ranks third.

Eleven countries have at least double the number of billionaires they had a year ago, including China, India, Turkey and South Korea.

Fourth placed Mukesh Ambani with a fortune of $29 billion has global ambitions, Forbes said. So has his younger brother Anil Ambani ranked 36 with a $13.7 billion fortune.

Fifth ranked Lakshmi Mittal with a fortune of $28.7 billion is "looking to expand in his native India; wants to build steel mills in Jharkhad and Orissa but has not received government approval," Forbes noted describing him as "London’s richest resident" who oversees ArcelorMittal, world’s largest steel maker

Shashi & Ravi Ruia brothers took the 40th spot with a fortune of $13.0 billion. Their "$15 billion (revenues) Essar Group has weathered downturn and embarked on an expansion drive in all its businesses, including steel, oil and power."

Last among the Indians in top 50 was Savitri Jindal, ranked 44th, with a fortune of $12.2 billion. She took over as head of O.P. Jindal Group after her husband died in a helicopter crash in 2005.